JP2009287456A - Failure diagnostic device of exhaust gas throttle valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure diagnostic device of an exhaust gas throttle valve capable of surely determining failure of the exhaust gas throttle valve. <P>SOLUTION: While limiting exhaust gas by the exhaust gas throttle valve when forcedly regenerating a DPF (diesel particulate filter), a target intake air quantity tgtQa is calculated for each control mode of forced regeneration by a target intake air quantity calculation part 71, the target intake air quantity tgtQa corresponding to the currently executing control mode is selected by a selection part 72, the intake throttle valve is fed back by an intake throttle control part 62 based on variance ΔQ between the selected target intake air quantity tgtQa and an actual intake air quantity Qa and an error of flow rate characteristics of the exhaust throttle valve is compensated. Based on a control state of the intake throttle valve at this time, whether the exhaust throttle valve is failed or not and failure content are determined by a failure diagnostic part 63. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust throttle valve failure diagnosis device, and more particularly to an exhaust throttle valve failure diagnosis device that limits the exhaust flow rate of an engine and raises the temperature of a DPF (diesel particulate filter) provided in an exhaust passage. is there.

For example, in an internal combustion engine that burns at a lean air-fuel ratio such as a diesel engine, the exhaust gas contains a large amount of particulates in addition to HC, CO, and NOx, and is used as a post-processing device for treating the particulates. An exhaust gas purification device that collects particulates in exhaust gas in a DPF has been put into practical use. In such an exhaust purification device, since it is necessary to incinerate and remove the particulates collected in the DPF, an oxidation catalyst is disposed upstream of the particulate filter, and the oxidation catalyst generates the NO from the exhaust gas. The so-called continuous regeneration is performed by continuously burning the particulates on the filter using NO ₂ as an oxidizing agent.

  Particulate incineration removal by continuous regeneration is naturally performed even during normal operation if the DPF temperature is equal to or higher than a predetermined value. However, if the operation state in which this condition is not satisfied continues, the amount of particulates collected by the DPF is allowed. It will fall into over-deposition beyond capacity. Therefore, forced regeneration is performed to regenerate the DPF by incineration removal of the particulates by aggressively raising the temperature of the DPF before over-deposition occurs. For example, it is supplied by post injection in the expansion stroke after the main injection. The burned unburnt fuel is burned on the upstream side oxidation catalyst, and the DPF located on the downstream side is heated to burn the particulates.

If the function of the above DPF is impaired, problems such as particulate discharge to the atmosphere occur, and therefore, for example, a countermeasure described in Patent Document 1 has been proposed. The technique of Patent Document 1 makes a failure determination that a DPF breakage or a functional failure has occurred when a particulate amount of a predetermined amount or more is detected by a soot sensor provided on the downstream side of the DPF.
JP 2007-315275 A

By the way, at the time of forced regeneration of the DPF, there is a case where an exhaust throttle valve provided in the exhaust passage of the engine is closed for the purpose of accelerating the temperature rise of the DPF. The effect of promoting the temperature rise of the DPF is obtained by utilizing the increase in the fuel injection amount to compensate for the decrease in rotation.
If this type of exhaust throttle valve breaks down, not only can the efficient forced regeneration by promoting the temperature rise of the DPF not be desired, but if the failure is due to the exhaust throttle valve being closed and closed, excessive exhaust restriction will cause engine damage, etc. Since a serious malfunction occurs, it is necessary to accurately diagnose the malfunction of the exhaust throttle valve and take prompt measures such as repair.

  However, it has been conventionally performed to determine the abnormality by monitoring the temperature rise state of the DPF. In addition to the post injection and the exhaust throttle control, the DPF temperature rise includes intake throttle control and ignition timing. Since various controls such as retard are used together, it is not possible to identify which control is the cause of the temperature rise abnormality, and it is inevitably impossible to directly determine the failure of the exhaust throttle valve, and prompt action can be expected. There wasn't. Naturally, the technique of the above-mentioned Patent Document 1 that determines the failure of the DPF itself cannot determine the failure of the exhaust throttle valve and cannot be a solution.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an exhaust throttle valve failure diagnosis device that can reliably determine an exhaust throttle valve failure. is there.

  In order to achieve the above object, according to the first aspect of the present invention, a filter for collecting particulates contained in the exhaust gas is disposed in the exhaust passage of the engine, and when the amount of particulate collection of the filter reaches a predetermined value. Executes forced regeneration to raise the temperature of the filter by increasing the exhaust temperature of the engine while controlling the exhaust throttle valve arranged in the exhaust passage by the forced regeneration control means, and incinerates and removes particulates collected by the filter. In an exhaust purification system for an engine, an intake throttle valve that is arranged in an intake passage of the engine and can adjust intake air flowing through the intake passage, and a forced regeneration calculated based on an operating state of the engine at the time of forced regeneration Intake throttle control means for feedback control of the opening of the intake throttle valve so as to reduce the deviation between the target intake air amount at the time and the actual intake air amount, During, based on the control status of the intake throttle valve by the intake throttle control means, in which a determining failure determining means the failure of the exhaust throttle valve.

  Therefore, the exhaust restriction by the exhaust throttle valve indirectly limits the intake air amount of the engine, so if the flow characteristic of the exhaust throttle valve causes an error with respect to the intended setting for some reason, The amount of intake air varies depending on the error. The actual intake air intake amount of the engine is adjusted to the target intake air amount set as the optimum value during forced regeneration by feedback control of the intake throttle valve, and as a result, errors in the flow rate characteristics of the exhaust throttle valve are compensated. Appropriate exhaust restriction.

  The control status of the intake throttle valve at this time reflects an error that has occurred in the flow characteristics of the exhaust throttle valve, and thus the failure of the exhaust throttle valve that caused the error. As an index indicating the control status, for example, a deviation between the target intake air amount and the actual intake air amount, or an operation amount of the intake throttle valve is set, and it becomes possible to reliably determine the failure of the exhaust throttle valve based on these indexes. .

According to a second aspect of the present invention, in the first aspect, when the failure determination means performs a forced regeneration and the deviation between the target intake air amount and the actual intake air amount is equal to or greater than a predetermined open adhesion determination value, This is to make a failure judgment due to the open throttle of the exhaust throttle valve.
Accordingly, when the exhaust throttle valve is open and stuck and exhaust restriction is not performed, even if the intake throttle valve is controlled to the closed side, it cannot be compensated for, so the deviation between the target intake air amount and the actual intake air amount is zero. It becomes a large value that is far away, and inevitably exceeds the open adhesion determination value. Therefore, in such a control state of the intake throttle valve, it can be regarded as a failure due to the open sticking of the exhaust throttle valve, and a failure determination due to the open sticking is made.

  The invention of claim 3 further comprises operation amount determination means for determining the operation amount of the intake throttle valve with the opening of the intake throttle valve before forced regeneration as the original position in claim 1, When the absolute value of the intake throttle valve operation amount determined by the operation amount determination means is equal to or greater than a preset individual difference determination value during the forced regeneration of the engine, the failure determination caused by the individual difference of the exhaust throttle valve Is something that

  Therefore, when the exhaust throttle valve has individual differences due to manufacturing errors or assembly errors to the vehicle body, the actual intake air amount is insufficient relative to the target intake air amount compared to the case where there is no individual difference. Alternatively, the intake throttle valve is controlled to be excessive and reduce the deviation. As a result, the operation amount of the intake throttle valve from the original position becomes a value of a certain amount on the positive side or the negative side, and the absolute value of the operation amount inevitably exceeds the individual difference determination value. Therefore, in such a control state of the intake throttle valve, it can be regarded as a failure due to an individual difference of the exhaust throttle valve, and a failure determination due to the individual difference is made.

  The invention of claim 4 further comprises operation amount determination means for determining the operation amount of the intake throttle valve with the opening of the intake throttle valve before forced regeneration as the original position in claim 1, wherein the failure determination means includes During regeneration, when the operation amount to the open side of the intake throttle valve determined by the operation amount determination means is equal to or greater than a predetermined particulate accumulation determination value, a failure caused by particulate accumulation of the exhaust throttle valve Judgment is made.

  Therefore, the amount of particulates accumulated on the exhaust throttle valve gradually increases with the engine operation time, and accordingly, the exhaust restriction by the exhaust throttle valve during forced regeneration becomes larger even with the same control amount. Inevitably, in order to compensate for an error in the flow rate characteristic, the intake throttle valve is gradually controlled to the open side, and the operation amount from the original position increases to become equal to or higher than the particulate deposition determination value at any point in time. Therefore, in such a control state of the intake throttle valve, it can be regarded as a failure due to the accumulation of particulates on the exhaust throttle valve, and a failure determination due to the accumulation of particulates is made.

  The invention of claim 5 further comprises operation amount determination means for determining the operation amount of the intake throttle valve with the opening of the intake throttle valve before forced regeneration as the original position in claim 1, wherein the failure determination means includes During regeneration, when the operation amount to the closing side of the intake throttle valve determined by the operation amount determination means is equal to or greater than a predetermined corrosion hole determination value, it is caused by a hole due to corrosion of the exhaust throttle valve. It makes a failure judgment.

  Therefore, if the exhaust throttle valve is punctured due to corrosion and gradually increases each time forced regeneration is performed, the exhaust restriction by the exhaust throttle valve during forced regeneration becomes smaller even with the same control amount. . Inevitably, in order to compensate for an error in the flow rate characteristic, the intake throttle valve is gradually controlled to the closed side, and the manipulated variable from the original position increases to reach the corrosion perforated determination value at some point. Therefore, in such a control state of the intake throttle valve, it can be regarded as a hole failure due to corrosion of the exhaust throttle valve, and a failure determination due to the hole of the exhaust throttle valve is made.

  According to a sixth aspect of the present invention, in the first aspect, the intake throttle control means delays the stop of the intake throttle valve feedback control for a predetermined time with respect to the stop of the exhaust throttle valve closing control at the end of the forced regeneration, thereby causing a failure. When the determination means is within a predetermined time and the absolute value of the deviation between the target intake air amount and the actual intake air amount is less than a preset closed sticking judgment value, the fault judgment due to the closed sticking of the exhaust throttle valve is determined. It is what

  Therefore, when the exhaust throttle valve is normally closed without closing and sticking within a predetermined time after the stop control of the exhaust throttle valve is stopped and the exhaust restriction is finished, the intake air amount rapidly increases and the control is continued. Even if the intake throttle valve inside is controlled to the closed side, it cannot be compensated for, so the deviation between the target intake air amount and the actual intake air amount exceeds the closed sticking judgment value, but the exhaust throttle valve sticks closed. When the exhaust restriction does not end, the deviation between the actual intake air amount and the target intake air amount is kept substantially zero by the intake throttle valve that is continuing control, and inevitably becomes less than the closed sticking determination value. Therefore, in such a control state of the intake throttle valve, it can be regarded as a failure due to the closed sticking of the exhaust throttle valve, and a failure determination due to the closed sticking is made.

According to a seventh aspect of the present invention, in the third, fourth, and sixth aspects, when the failure determination means makes a failure determination of the exhaust throttle valve, execution of the limp home mode in which the fuel injection amount is decreased with respect to the engine is performed. It is a command.
Therefore, when the exhaust throttle valve is closed and stuck, there is a risk that the exhaust will be unnecessarily restricted and the engine may be damaged. If the exhaust throttle valve has individual differences in the direction of shortage of the intake air amount, or the exhaust throttle valve Even when particulates are accumulated on the surface, there is a risk of engine damage due to unnecessary exhaust restriction. At this time, the limp home mode in which the fuel injection amount is reduced is executed to reduce the engine load, so that a more serious failure such as breakage can be avoided in advance.

According to an eighth aspect of the present invention, in the third, fourth, sixth, and seventh aspects, when the failure determination means makes a failure determination of the exhaust throttle valve, the engine is prohibited from being restarted.
Therefore, when the exhaust throttle valve is closed and stuck, there is a risk that the exhaust will be unnecessarily restricted and the engine may be damaged. If the exhaust throttle valve has individual differences in the direction of shortage of the intake air amount, or the exhaust throttle valve Even when particulates are accumulated on the surface, there is a risk of engine damage due to unnecessary exhaust restriction. At this time, restart of the engine is prohibited, so that a more serious failure such as breakage can be avoided in advance.

As described above, according to the exhaust purification device for an engine of the first aspect of the present invention, an error occurring in the flow characteristic of the exhaust throttle valve is compensated by the flow control on the intake throttle valve side, and the control of the intake throttle valve at this time is performed. By determining the failure of the exhaust throttle valve based on the situation, it is possible to reliably determine the failure that has occurred in the exhaust throttle valve.
According to the engine exhaust gas purification apparatus of the second aspect of the present invention, in addition to the first aspect, it is possible to reliably determine a failure caused by the open sticking of the exhaust throttle valve.

According to the engine exhaust gas purification apparatus of the third aspect of the present invention, in addition to the first aspect, it is possible to reliably determine a failure caused by an individual difference of the exhaust throttle valve.
According to the exhaust emission control device for an engine of the fourth aspect of the invention, in addition to the first aspect, it is possible to reliably determine a failure caused by the accumulation of particulates.
According to the engine exhaust gas purification apparatus of the fifth aspect of the present invention, in addition to the first aspect, it is possible to reliably determine a failure caused by a hole due to corrosion of the exhaust throttle valve.

According to the engine exhaust gas purification apparatus of the sixth aspect of the present invention, in addition to the first aspect, it is possible to reliably determine a failure caused by the closed adhering of the exhaust throttle valve.
According to the engine exhaust gas purification apparatus of the seventh aspect of the invention, in addition to the third, fourth, and sixth aspects, by executing the limp home mode when determining the exhaust throttle valve failure, a more serious failure such as engine breakage Can be avoided in advance.

  According to the engine exhaust gas purification apparatus of the eighth aspect of the invention, in addition to the third, fourth, sixth, and seventh aspects, by prohibiting the engine from restarting at the time of determining the exhaust throttle valve failure, Serious failure can be avoided in advance.

Hereinafter, an embodiment of a failure diagnosis device for an exhaust throttle valve embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing a failure diagnosis device for an exhaust throttle valve according to the present embodiment. The engine 1 is configured as an in-line 6-cylinder diesel engine. Each cylinder of the engine 1 is provided with a fuel injection valve 2, and each fuel injection valve 2 is supplied with pressurized fuel from a common common rail 3 and is opened at a timing according to the operating state of the engine. The fuel is injected into the inside.

  An intake manifold 4 is mounted on the intake side of the engine 1. An intake passage 5 connected to the intake manifold 4 is provided with an air flow sensor 6 that detects an intake air amount Qa from the upstream side, a compressor 7 a of a turbocharger 7, and an intercooler 8. An intake throttle valve 9 that is opened and closed by an actuator 9a is provided. An exhaust manifold 10 is mounted on the exhaust side of the engine 1, and an exhaust passage 11 is connected to the exhaust manifold 10 via a turbine 7b of a turbocharger 7 connected coaxially with the compressor 7a.

  During operation of the engine 1, the intake air introduced into the intake passage 5 through the air flow sensor 6 is pressurized by the compressor 7 a of the turbocharger 7 and then distributed to each cylinder through the intercooler 8, the intake throttle valve 9, and the intake manifold 4. Then, it is introduced into the cylinder in the intake stroke of each cylinder. In the cylinder, fuel is injected from the fuel injection valve 2 at a predetermined timing and ignited and burned in the vicinity of the compression top dead center, and the exhaust gas after combustion rotates through the exhaust manifold 10 and then rotates the turbine 7b and then passes through the exhaust passage 11. It is discharged outside.

  On the other hand, the intake manifold 4 and the exhaust manifold 10 are connected by an EGR passage 17, and an EGR valve 18 and an EGR cooler 19 that are opened and closed by an actuator 18 a are provided in the EGR passage 17. During operation of the engine 1, part of the exhaust gas is recirculated as EGR gas from the exhaust manifold 10 side to the intake manifold 4 side according to the opening degree of the EGR valve 18.

  The exhaust passage 11 is configured by connecting an upstream casing 31 and a downstream casing 32 to each other by pipes 33a to 33c. An upstream casing 31 is connected to the turbine 7b of the turbocharger 7 via a first pipe 33a, and the upstream casing 31 is connected to a downstream casing 32 via a second pipe 33b. The downstream casing 32 is connected to the silencer via the third pipe 33c, and the rear end of the silencer is open to the atmosphere.

A upstream oxidation catalyst 34 is accommodated in the upstream side of the upstream casing 31, and a wall flow type DPF (diesel particulate filter) 35 is accommodated in the downstream side. The DPF 35 acts to collect particulates in the exhaust gas. When the exhaust gas temperature of the engine 1 is relatively high, NO ₂ is generated from the NO in the exhaust gas by the oxidizing action of the pre-stage oxidation catalyst 34, and the NO ₂ The particulates collected in the DPF 35 by the oxidation reaction are continuously incinerated and removed, whereby the DPF 35 is regenerated.

A spray diffusion chamber 36 is formed on the downstream side of the DPF 35 in the upstream casing 31. A fin device 37 is installed in the spray diffusion chamber 36, and the fin device 37 causes a swirl flow in the exhaust gas by a large number of fins 37a.
An injection nozzle 38 is installed on the downstream side of the fin device 37 in the spray diffusion chamber 36, and the injection nozzle 38 arbitrarily injects the urea water pumped from a tank (not shown) into the spray diffusion chamber 36 as a reducing agent. It has become. A temperature sensor 39 is installed between the fin device 37 and the injection nozzle 38, and the exhaust gas temperature Tnzl in the spray diffusion chamber 36 is detected by the temperature sensor 39.

An SCR catalyst 40 (selective reduction type NOx catalyst) is accommodated on the upstream side in the downstream casing 32, and a post-stage oxidation catalyst 41 is accommodated on the downstream side. The SCR catalyst 40 acts to purify NOx in the exhaust gas. Play.
On the other hand, an input / output device (not shown), a storage device (ROM, RAM, etc.) used for storage of a control program, a control map, etc., a central processing unit (CPU), a timer counter, etc. Control unit) 51 is installed. On the input side of the ECU 51, the air flow sensor 6, the temperature sensor 39, the rotational speed sensor 52 that detects the engine rotational speed Ne, and the intake O ₂ concentration that is provided in the cylinder of each cylinder are provided in the intake manifold 4. An intake O ₂ sensor 53 to detect, a catalyst temperature sensor 54 to detect the temperature Tcat of the SCR catalyst 40, an accelerator sensor 55 to detect the accelerator operation amount Acc, a NOx sensor 56 to detect the NOx emission amount on the downstream side of the SCR catalyst 40, Various sensors such as an opening degree sensor 57 for detecting the opening degree θ of the intake throttle valve 9 are connected. Further, on the output side of the ECU 51, the intake throttle valve 9, the exhaust throttle valve 12, the actuators 9a, 12a, 18a of the EGR valve 18, the fuel injection valve 2, the injection nozzle 38, and a warning lamp 58 provided in the driver's seat. Etc. are connected.

  For example, the ECU 51 sets the fuel injection amount Q according to a predetermined map from the engine rotation speed Ne and the accelerator operation amount Acc, and sets the fuel injection timing IT according to a predetermined map from the fuel injection amount Q and the engine rotation speed Ne. The fuel injection valve 2 is driven and controlled based on the fuel injection amount Q and the fuel injection timing IT, and the engine 1 is operated by injecting fuel into the cylinder of each cylinder.

The ECU 51 controls the injection amount of urea water from the injection nozzle 38 based on the exhaust gas temperature Tnzl detected by the temperature sensor 39. The injected urea water is hydrolyzed by exhaust heat and water vapor in the exhaust gas to generate ammonia (NH ₃ ), and on this SCR catalyst 40, NOx in the exhaust gas is reduced to harmless N ₂ on the SCR catalyst 40. While purification is performed, surplus ammonia at this time is oxidized to NO by the post-stage oxidation catalyst 41.

Further, the ECU 51 appropriately executes forced regeneration in order to maintain the purification function of the DPF 35 (forced regeneration control means). That is, when the temperature of the DPF 35 is lowered due to low speed traveling due to traffic jams or a decrease in the outside air temperature due to cold regions, the amount of particulates collected by the DPF 35 exceeds the allowable amount without obtaining the above-mentioned continuous regeneration action. Will fall into excessive deposition. Therefore, for example, when the particulate collection amount obtained from the differential pressure across the DPF 35 reaches a predetermined regeneration start determination value, the ECU 51 raises the DPF 35 to forcibly regenerate the particulates by incineration and removal. Execute. Note that HC and CO generated during particulate combustion by forced regeneration are oxidized to CO ₂ by the post-stage oxidation catalyst 41.

  Forced regeneration is broadly divided into automatic regeneration and manual regeneration. In normal operation, automatic regeneration is performed during vehicle travel to raise the temperature of the DPF 35. On the other hand, automatic regeneration due to continuous low speed travel or the like cannot sufficiently raise the DPF 35 sufficiently. In some cases, after the driver is prompted to stop, manual regeneration is performed while operating the engine 1 under the optimum conditions for increasing the temperature of the DPF 35 in response to the operation of a start button (not shown) by the driver. Any forced regeneration is realized by post-injection after main injection, EGR control, control of fuel injection timing IT and injection pressure, valve closing control of the exhaust throttle valve 12, etc., but it is controlled by automatic regeneration and manual regeneration. In addition to the difference in content, in any forced regeneration, the DPF 35 temperature rise process (for example, the preliminary temperature rise control for raising the DPF 35 from the normal temperature, and alternately executed after the preliminary temperature rise control to bring the DPF 35 to the target temperature) The contents of control differ depending on the ascending control and descending control to be held.

  However, since there is a certain amount of error in the flow rate characteristics of the exhaust throttle valve 12, the actual flow characteristics differ from the expected flow characteristics of the exhaust throttle valve 12, and an inappropriate exhaust restriction is caused. As a result, there is a possibility that a problem such as prolonging the time required for forced regeneration may occur. As a countermeasure, in the present embodiment, a countermeasure is taken to compensate for an error in the flow characteristic due to the exhaust throttle valve 12 by flow control on the intake throttle valve 9 side (intake throttle control means). Control executed for the intake throttle valve 9 will be described.

FIG. 2 is a flowchart showing an intake throttle control routine executed by the ECU 51. The ECU 51 executes the routine at a predetermined control interval.
First, it is determined in step S2 whether or not forced regeneration of the DPF 35 is being executed. If the determination is No (No), control of the normal intake throttle valve 9 is executed in step S4, and then the routine is temporarily terminated. . When the determination in step S2 is Yes (positive), the process proceeds to step S6 to determine the forced regeneration control mode. As described above, the control mode is set in advance corresponding to each temperature increase process of automatic regeneration and manual regeneration, and in step S6, the currently executed control mode is determined. Next, in step S8, flow characteristic compensation control is executed, and then the routine ends.

  The flow rate characteristic compensation control performs feedback control of the opening degree of the intake throttle valve 9 in order to compensate for an error in the flow rate characteristic of the exhaust throttle valve 12, and the processing executed by the ECU 51 for the flow rate characteristic compensation control is shown in FIG. Show the procedure. As shown in this figure, the ECU 51 includes a command value setting unit 61 and an intake throttle control unit 62 as a configuration for executing the flow rate characteristic compensation control. The command value setting unit 61 performs a function of calculating a command value related to the control of the intake throttle valve 9 necessary to compensate for an error in the flow rate characteristic due to the exhaust throttle valve 12, and the intake throttle control unit 62 The actuator 9a is driven and controlled.

  First, the command value setting unit 61 will be described. The target intake air amount calculation unit 71 calculates the target intake air amount tgtQa based on the engine speed Ne and the fuel injection amount Q according to a map set for each forced regeneration control mode. In forced regeneration, there is an optimum intake air amount for achieving the temperature rise state of the DPF 35 assumed in each control mode, and each map characteristic is derived so as to derive this optimum intake air amount as the target intake air amount tgtQa. From these maps, the target intake air amount tgtQa based on the current operating state of the engine 1 is calculated for each control mode.

  The target intake air amount tgtQa of each control mode calculated by the target intake air amount calculation unit 71 is input to the selection unit 72, and the selection unit 72 selects the target intake air amount tgtQa corresponding to the currently executed control mode. . The selected target intake air amount tgtQa is input to the deviation calculating unit 73 together with the actual intake air amount Qa detected by the air flow sensor 6, and the deviation ΔQ of both is calculated.

The above is the process executed by the command value setting unit 61, and the calculated deviation ΔQ is input to the intake throttle control unit 62. In the intake throttle control unit 62, the control amount of the intake throttle valve 9 is calculated by PID control based on the input deviation ΔQ, and the opening degree θ of the intake throttle valve 9 is feedback controlled based on the calculated control amount.
With the above flow characteristic compensation control, the actual intake air amount Qa of the engine 1 is always adjusted to the target intake air amount tgtQa in any control mode during forced regeneration. Exhaust restriction by the exhaust throttle valve 12 indirectly restricts the intake air amount Qa of the engine 1, so that the target intake air amount tgtQa should be achieved if there is no error in the flow characteristic of the exhaust throttle valve 12. On the other hand, if there is an error in the flow characteristics of the exhaust throttle valve 12, the intake air amount Qa varies according to the error. Therefore, by adjusting the actual intake air amount Qa to the target intake air amount tgtQa by the flow rate characteristic compensation control, it is possible to compensate for an error that has occurred in the flow rate characteristic of the exhaust throttle valve 12 as a result. An appropriate exhaust restriction similar to that in the case where no error has occurred can be realized, and stable forced regeneration can be realized.

  On the other hand, since the error in the flow rate characteristic of the exhaust throttle valve 12 is compensated by the flow rate characteristic compensation control, the operation can be continued as it is. However, an error in the flow characteristic occurs due to various factors. For example, if an error in the flow characteristic occurs due to an individual difference such as a manufacturing error of the exhaust throttle valve 12 or an assembly error to the vehicle body, Replacement of the throttle valve 12, reassembly / adjustment to the vehicle body, etc. should be carried out, and if there is an error in the flow characteristics due to aging due to accumulation of particulates, exhaust The throttle valve 12 should be disassembled and cleaned, and in order to perform such measures, it is necessary to diagnose the exhaust throttle valve 12 and warn the driver.

Further, for example, when the exhaust throttle valve 21 is fixed open, complete compensation is difficult in the flow characteristic compensation control, so that sufficient exhaust gas temperature cannot be expected, and when the exhaust throttle valve 12 is fixed closed, the flow rate The characteristic compensation control cannot cope with this, and there is a risk of damage due to a sudden increase in engine load. Therefore, in order to avoid these problems, failure diagnosis of the exhaust throttle valve 12 is necessary.
Therefore, the ECU 51 includes a failure diagnosis unit 63 that diagnoses the presence or absence and details of the failure of the exhaust throttle valve 21 and warns the driver based on the diagnosis result. The fault diagnosis to be executed will be described.

FIG. 4 is a flowchart showing a failure diagnosis routine executed by the ECU 51. The ECU 51 executes the routine at a predetermined control interval.
First, it is determined in step S12 whether or not forced regeneration of the DPF 35 has been completed. If forced regeneration is still being executed, a determination of No is made and the process proceeds to step S14. In step S14, it is determined whether or not the deviation ΔQ between the target intake air amount tgtQa and the actual intake air amount Qa is equal to or larger than a preset open adhesion determination value ΔQ1. The determination process includes failure of the exhaust throttle valve 12 to be stuck open (including not only the original open sticking when the valve is stuck in the valve open state but also the malfunction in the valve open state due to air leakage or the like). (Failure determination means). FIG. 5 is a time chart showing the exhaust restriction state when the exhaust throttle valve 12 is stuck open. As shown by the solid line in the figure, the exhaust throttle valve 12 is normally closed without being stuck open. When exhaust restriction is performed, the actual intake air amount Qa rapidly decreases and substantially coincides with the target intake air amount tgtQa set in the flow rate characteristic compensation control.

  On the other hand, as shown by the broken line in the figure, when the exhaust throttle valve 12 is fixed open and exhaust restriction is not performed, the actual intake air amount Qa does not decrease at all or only decreases slightly. In response to this, even if the intake throttle valve 9 is controlled to the closed side by the flow characteristic compensation control, the hatching region where the actual intake air amount Qa should be increased cannot be compensated for, so the target intake air amount tgtQa and the actual intake air The deviation ΔQ from the air amount Qa is a large value far from 0, and is necessarily equal to or larger than the open adhesion determination value ΔQ1.

When the exhaust throttle valve 12 is not openly stuck and the deviation ΔQ is less than the open sticking determination value ΔQ1, the ECU 51 makes a determination of No in step S14 and proceeds to step S16.
In step S16, it is determined whether or not the absolute value of the operation amount Δθ of the intake throttle valve 9 is equal to or greater than a preset individual difference determination value Δθ1. The manipulated variable Δθ means a change amount of the opening θ with the opening θ of the intake throttle valve 9 before forced regeneration as the original position. In the present embodiment, the original position is set between the fully open position and the fully closed position, and the intake throttle valve 9 is controlled in both the open side and the close side in the flow characteristic compensation control around this original position. For convenience, the operation amount Δθ to the opening side of the intake throttle valve 9 is set to a positive value, and the operation amount Δθ to the closing side of the intake throttle valve 9 is set to a negative value. The operation amount Δθ is calculated based on the opening θ of the intake throttle valve 9 detected by the opening sensor 57, and the determination in step S16 is performed based on the calculated operation amount Δθ (operation amount determination means).

  The determination process of step S16 determines an individual difference of the new exhaust throttle valve 12 as a failure (failure determination means). FIG. 6 is a time chart showing the exhaust restriction status when the exhaust throttle valve 12 has individual differences. The exhaust throttle valve 12 has unacceptable individual differences due to manufacturing errors and assembly errors to the vehicle body. In this case, the actual intake air amount Qa is insufficient or excessive with respect to the target intake air amount tgtQa as shown by the broken line as compared with the case where there is no individual difference indicated by the solid line in the figure, and the hatching region is compensated. Therefore, the opening degree θ of the intake throttle valve 9 is controlled so as to reduce the deviation ΔQ. As a result, the operation amount Δθ of the intake throttle valve 9 has a value of a certain amount on the positive side or the negative side, and the absolute value of the operation amount Δθ necessarily becomes the individual difference determination value Δθ1 or more.

  When such an individual difference of the exhaust throttle valve 12 does not occur and the absolute value of the operation amount Δθ is less than the individual difference determination value Δθ1, the ECU 51 makes a determination of No in step S16 and proceeds to step S18. Since individual differences have already occurred in the new exhaust throttle valve 12, the determination process in step S16 is executed only at the first forced regeneration when the new vehicle starts operation, and is unconditional at the second and subsequent forced regenerations. No is determined to mean no failure due to individual differences.

  In step S18, it is determined whether or not the operation amount Δθ of the intake throttle valve 9 is equal to or greater than the particulate accumulation determination value Δθ2 set in advance as a positive side (open side) value. The determination process determines a change in the flow characteristic (flow reduction direction) of the exhaust throttle valve 12 accompanying the accumulation of particulates as a failure (failure determination means). FIG. 7 is a time chart showing the exhaust restriction status at each forced regeneration when particulates accumulate on the exhaust throttle valve 12, and the amount of particulates deposited on the exhaust throttle valve 12 gradually increases with the engine operation time. Accordingly, the exhaust restriction by the exhaust throttle valve 12 during forced regeneration becomes larger even with the same control amount, and the actual intake air amount Qa gradually becomes insufficient with respect to the target intake air amount tgtQa. In order to inevitably compensate for the hatching region, the intake throttle valve 9 is gradually controlled to open side every time the forced regeneration is executed, and the operation amount Δθ increases to the positive side, and the particulate accumulation determination is performed at any time. The value Δθ2 or more.

When the accumulation of particulates on the exhaust throttle valve 12 has not yet progressed, and the operation amount Δθ of the intake throttle valve 9 is less than the particulate accumulation determination value Δθ2, the ECU 51 makes a No determination in step S18. Then, the process proceeds to step S20.
In step S20, it is determined whether or not the operation amount Δθ of the intake throttle valve 9 is less than the corrosion perforation determination value Δθ3 set in advance as a negative (closed) value. The determination process is to determine a change in the flow characteristic (flow increasing direction) of the exhaust throttle valve 12 due to a hole due to corrosion of the exhaust throttle valve 12 as a failure (failure determination means). FIG. 8 is a time chart showing the exhaust restriction status at each forced regeneration when the exhaust throttle valve 12 is punctured due to corrosion, and the holes gradually expand with the progress of corrosion, and the exhaust at the forced regeneration is accompanied accordingly. The exhaust restriction by the throttle valve 12 becomes smaller even with the same control amount, and the actual intake air amount Qa gradually becomes excessive with respect to the target intake air amount tgtQa. Inevitably, in order to compensate for the hatching area, the intake throttle valve 9 is gradually controlled to the closed side every time the forced regeneration is executed, and the operation amount Δθ increases to the negative side, and the corrosion hole is determined at any time. The value is less than Δθ3.

When there is no hole due to such corrosion, or even if there is a hole, the ECU 51 determines No in step S20 when the operation amount Δθ of the intake throttle valve 9 is equal to or greater than the corrosion hole determination value Δθ3. To finish the routine.
On the other hand, when the forced regeneration of the DPF 35 ends and the determination in step S12 is Yes, the ECU 51 proceeds to step S22. In step S22, it is determined whether or not the absolute value of the deviation ΔQ between the target intake air amount tgtQa and the actual intake air amount Qa is less than the closed sticking determination value ΔQ2. As the forced regeneration is finished, the exhaust throttle valve 12 is stopped from the valve closing control and returned to full open, and the intake throttle valve 9 is stopped from the flow characteristic compensation control and returned to the original position before the forced regeneration. In the flow characteristic compensation control in order to execute the determination process of S22, the stop of the feedback control for the intake throttle valve 9 is delayed by a predetermined time with respect to the stop of the valve closing control for the exhaust throttle valve 12, and within this predetermined time. In step S22, the determination process is executed.

  The determination process determines that the exhaust throttle valve 12 is stuck closed as a failure (failure determination means). FIG. 9 is a time chart showing the exhaust restriction state when the exhaust throttle valve 12 is closed and stuck, and as shown by the solid line in the figure, the exhaust throttle valve 12 is normally opened without being closed and stuck. When the exhaust restriction is finished, the intake air amount Qa rapidly increases, and even if the intake throttle valve 9 is controlled to be closed by the ongoing flow characteristic compensation control, the hatching region where the actual intake air amount Qa should be reduced is compensated. Therefore, the absolute value of the deviation ΔQ between the target intake air amount tgtQa and the actual intake air amount Qa is equal to or greater than the closed sticking determination value ΔQ2.

  On the other hand, when the exhaust throttle valve 12 is closed and stuck and exhaust restriction does not end, the actual intake air amount Qa continues to decrease as shown by the broken line, even if there is an error in the flow rate characteristic of the exhaust throttle valve 12. (The figure shows the case of Qa = tgtQa with no error.) The absolute value of the deviation ΔQ between the actual intake air amount Qa and the target intake air amount tgtQa is kept at almost 0 by the ongoing flow rate characteristic compensation control, and inevitably Therefore, it becomes less than the closed sticking determination value ΔQ2.

When the exhaust throttle valve 12 is not closed and the absolute value of the deviation ΔQ is equal to or larger than the closed fixation determination value ΔQ2, the ECU 51 determines No in step S22 and ends the routine.
On the other hand, when the exhaust throttle valve 12 is stuck open and a Yes determination is made in step S14, the process proceeds to step S24. In step S24, diagnostic data indicating that the exhaust throttle valve 12 is stuck open is stored, and after the warning lamp 58 is turned on in the subsequent step S26, the routine is terminated.

If YES is determined in step S16 as the individual difference of the exhaust throttle valve 12, diagnostic data indicating the individual difference of the exhaust throttle valve 12 is stored in step S28, and the process proceeds to step S26.
Further, when Yes is determined in step S18 as the accumulation of particulates on the exhaust throttle valve 12, diagnostic data indicating the accumulation of particulates on the exhaust throttle valve 12 is stored in step S30, and the above step S26 is performed. Transition.

Further, if the exhaust throttle valve 12 is found to have a hole due to corrosion, a determination of Yes is made in step S20, the diagnostic data indicating the hole due to corrosion of the exhaust throttle valve 12 is saved in step S32, and step S26 described above. Migrate to
If the determination in step S22 is Yes for the closed tightness of the exhaust throttle valve 12, diagnostic data indicating the closed tightness of the exhaust throttle valve 12 is stored in step S34, and the process proceeds to step S26.

  When a failure occurs in the exhaust throttle valve 12 by the above-described failure diagnosis processing of the ECU 51, diagnostic data indicating the failure content is stored in the ECU 51, and a warning is given to the driver by turning on the warning lamp 58. Therefore, the driver who has recognized the occurrence of the failure promptly brings the vehicle to the maintenance shop and takes an appropriate countermeasure, and the repair operator can check the failure of the exhaust throttle valve 12 based on the diagnostic data read from the ECU 51 by the service tool. The contents can be grasped promptly and accurately. For example, in the conventional technology, even if a temperature increase abnormality of the DPF 35 occurs, it has not been possible to specify which of the various controls executed when the DPF 35 is heated. Of course, the exhaust throttle valve 12 is in failure, and the failure content can be specified. As a result, the repair worker can omit the extra work for finding out the content of the failure and immediately start repairing according to the content of the failure.

  For example, the exhaust throttle valve 12 can be fixed open by replacing the exhaust throttle valve 12 or checking and repairing the air line. For individual differences in the exhaust throttle valve 12, the exhaust throttle valve 12 can be replaced. It is dealt with by reassembling and adjusting to the vehicle body, and the accumulation of particulates on the exhaust throttle valve 12 is dealt with by disassembling and cleaning the exhaust throttle valve 12. Although the valve 12 is closed and fixed, it can be dealt with by exchanging the exhaust throttle valve 12. However, the inspection / repair according to the contents of each failure can be started immediately.

In addition, specifying the details of the failure of the exhaust throttle valve 12 is not only a matter of repair work, but the degree of influence on the vehicle travel can be estimated from the content of the failure, so that the vehicle travels from the occurrence of the failure to the repair according to the content of the failure. The inside control can be optimized.
Specifically, the closed adhering of the exhaust throttle valve 12 can be regarded as the most serious failure because exhaust restriction is unnecessarily performed other than during forced regeneration, and the engine may be damaged. Therefore, when it is determined in step S22 that the exhaust throttle valve 12 is closed and stuck, for example, the fuel injection amount of the engine 1 is corrected to decrease and switched to the limp home mode, and the engine 1 is once stopped and then restarted. (The driver is notified in advance of the prohibition of restart). As a result, even if the vehicle is driven with the exhaust throttle valve 12 closed and fixed, the engine load is reduced, and restarting after the engine is stopped is prevented, so that more serious failures such as engine breakage can be avoided in advance. can do.

  Further, the accumulation of particulates on the exhaust throttle valve 12 and individual differences on the closed side of the exhaust throttle valve 12 cause unnecessary exhaust restriction, which is not as close as the closed fixation, and cannot be compensated by the flow characteristic compensation control. there is a possibility. Therefore, when the individual difference of the exhaust throttle valve 12 is determined due to the generation of the positive operation amount Δθ in step S16, or when the accumulation of particulates is determined in step S18, the exhaust throttle valve 12 is closed. Similarly, if switching to limp home mode is performed and prohibition of restart is performed as necessary, engine damage can be avoided in advance.

  This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the exhaust purification device of an in-line 6-cylinder diesel engine is embodied. However, the DPF 35 is provided with a particulate collection DPF 35, and the exhaust throttle valve 12 disposed in the exhaust passage 11 is controlled to be closed. As long as it is an exhaust emission control device that performs forced regeneration, the engine type, control content of forced regeneration, and the like are not limited to this, and can be arbitrarily changed.

1 is an overall configuration diagram illustrating a failure diagnosis device for an exhaust throttle valve according to an embodiment. It is a flowchart which shows the intake throttle control routine which ECU performs. It is a block diagram which shows the process sequence which ECU performs for flow characteristic compensation control. It is a flowchart which shows the failure diagnosis routine which ECU performs. It is a time chart which shows the exhaust restriction condition when open sticking arises in an exhaust throttle valve. It is a time chart which shows the exhaust restriction condition when an exhaust throttle valve has an individual difference. It is a time chart which shows the exhaust restriction condition at the time of each forced regeneration when particulates accumulate on an exhaust throttle valve. It is a time chart which shows the exhaust restriction condition at the time of each forced regeneration when the hole by corrosion arises in the exhaust throttle valve. It is a time chart which shows the exhaust restriction condition when closed sticking arises in an exhaust throttle valve.

Explanation of symbols

1 Engine 5 Intake Passage 9 Intake Throttle Valve 11 Exhaust Passage 12 Exhaust Throttle Valve 35 DPF (Filter)
51 ECU (Forced regeneration control means)
61 Target intake air amount calculation unit (intake throttle control means)
62 Intake throttle control unit (Intake throttle control means)
63 Failure diagnosis unit (failure determination means, operation amount determination means)

Claims (8)

A filter for collecting particulates contained in the exhaust gas is disposed in the exhaust passage of the engine, and when the particulate collection amount of the filter reaches a predetermined value, it is disposed in the exhaust passage by the forced regeneration control means. In an exhaust purification system for an engine that performs forced regeneration to raise the temperature of the filter by raising the exhaust temperature of the engine while closing the exhaust throttle valve, and incinerating and removing the particulates collected by the filter,
An intake throttle valve which is disposed in the intake passage of the engine and can adjust intake air flowing through the intake passage;
During the forced regeneration, feedback control of the opening of the intake throttle valve is performed so as to reduce the deviation between the target intake air amount and the actual intake air amount calculated based on the operating state of the engine. Intake throttle control means for
An exhaust throttle valve failure diagnosis device comprising: failure determination means for determining a failure of the exhaust throttle valve based on a control state of the intake throttle valve by the intake throttle control means during the forced regeneration.   The failure determination means is caused by the open adhering of the exhaust throttle valve when a deviation between the target intake air amount and the actual intake air amount is equal to or larger than a predetermined open adhering determination value during execution of the forced regeneration. The failure diagnosis device for an exhaust throttle valve according to claim 1, wherein the failure determination is performed. An operation amount determination means for determining an operation amount of the intake throttle valve with an opening of the intake throttle valve before the forced regeneration as an original position;
The failure determination means, when the first forced regeneration is being executed, when the absolute value of the operation amount of the intake throttle valve determined by the operation amount determination means is equal to or greater than a preset individual difference determination value, The failure diagnosis device for an exhaust throttle valve according to claim 1, wherein a failure determination due to an individual difference of the valve is made. An operation amount determination means for determining an operation amount of the intake throttle valve with an opening of the intake throttle valve before the forced regeneration as an original position;
The failure determination unit is configured to execute the exhaust when the operation amount to the open side of the intake throttle valve determined by the operation amount determination unit is equal to or greater than a predetermined particulate accumulation determination value during execution of the forced regeneration. The failure diagnosis device for an exhaust throttle valve according to claim 1, wherein a failure determination due to particulate accumulation of the throttle valve is made. An operation amount determination means for determining an operation amount of the intake throttle valve with an opening of the intake throttle valve before the forced regeneration as an original position;
The failure determination means is configured to execute the exhaust when the operation amount to the closing side of the intake throttle valve determined by the operation amount determination means is equal to or greater than a predetermined corrosion perforation determination value during execution of the forced regeneration. The failure diagnosis device for an exhaust throttle valve according to claim 1, wherein a failure determination caused by a hole due to corrosion of the throttle valve is made. The intake throttle control means delays the stop of the feedback control of the intake throttle valve for a predetermined time with respect to the stop of the closing control of the exhaust throttle valve at the end of the forced regeneration,
The failure determination means is configured to close the exhaust throttle valve when the absolute value of the deviation between the target intake air amount and the actual intake air amount is less than a preset close adhesion determination value within the predetermined time. 2. The exhaust throttle valve failure diagnosis apparatus according to claim 1, wherein the failure determination is caused.   The failure determination means commands the engine to execute a limp home mode in which the fuel injection amount is reduced when a failure determination of the exhaust throttle valve is made. 6. The failure diagnosis device for an exhaust throttle valve according to any one of claims 6 to 10.   The said failure determination means commands the prohibition of restart to the engine when the failure determination of the exhaust throttle valve is made. Trouble diagnosis device for exhaust throttle valve.

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